Electrically switchable valley polarization, spin/valley filter, and valve effects in transition-metal dichalcogenide monolayers interfaced with two-dimensional ferromagnetic semiconductors

TL;DR

This paper introduces a novel method to control electron valleys in transition-metal dichalcogenide monolayers by coupling them directly to 2D ferromagnets, enabling electrically switchable valley polarization and spin/valley filtering effects for advanced device applications.

Contribution

It proposes a new approach to manipulate electron valleys via direct coupling to 2D ferromagnets, differing from previous proximity effect methods, and demonstrates this in specific heterojunctions using first-principles calculations.

Findings

Valley-selective gap opening due to spin-momentum locking.

Electrically switchable valley polarization achieved.

Realization of spin/valley filter and valve effects.

Abstract

Electron valleys in transition-metal dichalcogenide monolayers drive novel physics and allow designing multifunctional architectures for applications. We propose to manipulate the electron valleys in these systems for spin/valley filter and valve devices through band engineering. Instead of the magnetic proximity effect that has been extensively used in previous studies, in our strategy, the electron valleys are directly coupled to the spin-polarized states of the two-dimensional ferromagnets. We find that this coupling results in a valley-selective gap opening due to the spin-momentum locking in the transition-metal dichalcogenide monolayers. This physics gives rise to a variety of unexpected electronic properties and phenomena including halfmetallicity, electrically switchable valley polarization, spin/valley filter and valve effects in the transition-metal dichalcogenide monolayers. We further demonstrate our idea in MoTe$_2$/CoCl$_2$ and CoCl$_2$/MoTe$_2$/CoCl$_2$ van der Waals heterojunctions based on first-principles calculations. Thus, our study provides a way of engineering the electron valleys in transition-metal dichalcogenide monolayers for new-concept devices.